Projectors, projector assemblies, and other related devices are often used to provide images using a light source to project an image onto a surface, such as a screen or a wall. There are many different types of projectors used for many different purposes. For example, a video projector intakes a video signal from a device, such as a computer, home theater system, DVD player, etc. to project images from the video signal. Other examples of projectors include movie projectors to project moving pictures from a filmstrip, slide projectors to project still images on film media, or an overhead projector to project still images on a transparent sheet using a reflective base and lens. Images are projected using a light source.
To project images onto a surface such as wall, the light source may comprise a high wattage light bulb to provide enough light to project the image clearly on the wall from a certain distance. High wattage light bulbs not only emit sufficient light to project the image, but also generate a significant amount of heat. The heat generated by the high wattage light bulbs often leads to overheating of the light assembly and the projector, when a maximum threshold temperature is reached. Overheating, and consistent or continued use of the projector at a temperature exceeding the maximum threshold temperature, may cause damage to the light assembly, light bulb, or projector itself. Overheating also limits the amount of use, as a user may need to occasionally shut off the projector to allow it to cool down to an operating temperature before continuing. This may be very disruptive, particularly for video or movie projectors where continuity of the projected images is essential. Thus, a cooling system and method is needed to prevent overheating of the projector to reduce damage, and increase productivity, reliability, and product longevity by providing preferred operating conditions for the lamp assembly of the projector. As a result, maximum light output and maximum lifetime of the lamp are achieved in that light bulbs do not need to be changed as frequently, and the risk of the light bulbs exploding due to high temperatures is reduced.
However, because of natural convection, there may be differences in the temperature of gas inside the light bulb as the gas at the top of the light bulb will be significantly hotter than the gas at the bottom of the light bulb. Thus, providing a single, constant supply of air to the light source of the light assembly in a projector to cool the light bulb is also insufficient, as a temperature difference between the top and the bottom of the light bulb will still occur. Even with a constant supply of air through a fan or other means, hotter gas will still rise to the top of the light bulb, and cooler gas will still remain at the bottom of the light bulb. Air outside the light bulb but within the lamp assembly may be moved quickly past the bulb by the supply of air provided by the fans, thus not being affected strongly by natural convection. The temperature difference between the top and the bottom of the light bulb may also cause damage to the light bulb and reduce its longevity, thus a small temperature difference between the bulb top and bottom needs to be maintained for optimal performance, reliability, and product lifespan. Particularly for high wattage lamps used in projectors, the temperature difference between the top of the light bulb and the bottom of the light bulb should be as small as possible to prevent damage. Therefore, an improved cooling system to provide and maintain a small temperature difference, with minimal temperature variance is needed, and cannot be achieved with conventional cooling systems providing a single, symmetric supply of air.
Additionally, because the applications of projectors may differ, there are multiple configurations and mounting variations for a projector's particular use. For example, an overhead projector or slide projector is typically desktop-mounted so that slides, film, and transparencies may be accessed by a user, whereas a video projector may be desktop-mounted or ceiling-mounted, and connected to a DVD player through a cable. Projectors may also have multiple light assemblies and light sources with different configurations, for example, projectors capable of rotation around the lamp axis. These factors introduce complications in providing cooling solutions to projectors efficiently and universally, without incurring significant changes or costs to accommodate different mounting configurations and/or existing projector systems. Thus, specialized and improved cooling systems and methods are needed.
Embodiments of the invention address these and other problems.